It is well known that increasing the area ratio of a rocket engine nozzle can increase the amount of thrust which is produced using the same amount of fuel. However, various design factors limit the area ratio of a nozzle which can be readily accommodated. One of these factors is a limit to the overall nozzle length. One solution has been to provide an extendible nozzle which allows the nozzle length to be increased when the vehicle on which the rocket is mounted is deployed in space and letting the nozzle be retracted when the vehicle is stored or in stowed position.
The concept of an extendible nozzle is not new, one such arrangement, for example, being described in U.S. Pat. No. 3,951,342 in which a plurality of elongated petals are hinged to the exit portion of the main nozzle to form an extended nozzle section when rotated outwardly. However, such known extendible nozzle arrangements have suffered from one or more of the following problems, namely, they have entailed complex mechanisms for extending and retracting the nozzle, such mechanisms have been bulky and heavy or have not been sufficiently rugged to insure reliability under transfer loads, during gimbaling of the rocket engine, or buffeting of the vehicle. Also they have required complicated controls and sensing devices to deploy the nozzle extension and insure that it is locked in place.